Answer: With no choices given here, here are a few possibilities.
If it is not a right triangle, the third side could be any number less than 50 cm
If it is a right triangle, the third side could be the hypotenuse, which would be 10√13 or about 36.05 cm.
If 30cm is the hypotenuse, the other side would be 10√5 or about 22.36 cm
Step-by-step explanation: If the two given sides add up to 50, they flatten out to a straight line, equal to the third side, so it is no longer a triangle. The third side must be less than the sum of the other two sides.
We can use the Pythagorean Theorem a² + b² = c² to calculate the lengths of the sides of a right triangle.
For example
20² + 30² = c²
400 + 900 = c²
1300 = c²
√1300 = √(100)(13) = √c²
10√13 = c ≈ 36.05